Investing in mutual funds for retirement is never too late. And the Zacks Mutual Fund Rank can be an excellent tool for investors looking to invest in the best funds.

The easiest, most reliable way to judge a mutual fund's quality over time is by analyzing its performance, diversification, and fees. The Zacks Mutual Fund Rank, which covers over 19,000 mutual funds, has helped us identify three outstanding options that are perfect for any long-term investors' portfolios that is retirement-focused.

Let's learn about some of Zacks' highest ranked mutual funds with low fees you may want to consider.

Harbor Small Cap Growth Admiral

(HRSGX Quick QuoteHRSGX - Free Report) : 1.13% expense ratio and 0.75% management fee. HRSGX is a Small Cap Growth mutual fund and tends to feature small companies in up-and-coming industries and markets. With annual returns of 10.39% over the last five years, this fund is a winner.

Goldman Sachs US Equity Insights A

(GSSQX Quick QuoteGSSQX - Free Report) . Expense ratio: 0.92%. Management fee: 0.52%. GSSQX is classified as a Large Cap Blend fund. More often than not, Large Cap Blend mutual funds invest in companies with a market cap of over $10 billion. Buying stakes in bigger companies offer these funds more stability, and are well-suited for investors with a "buy and hold" mindset. This fund has managed to produce a robust 14.35% over the last five years.

TIAA-CREF Large Cap Growth Premier

(TILPX Quick QuoteTILPX - Free Report) : 0.56% expense ratio and 0.4% management fee. TILPX is a Large Cap Growth mutual fund, and these funds invest in many large U.S. firms that are projected to grow at a faster rate than their large-cap peers. With a five-year annual return of 16.19%, this fund is a well-diversified fund with a long track record of success.

These examples highlight the fact that there are some astonishingly good mutual funds out there. If your advisor has you in the good ones, bravo! If not, you may need to have a talk.